Ore no Shibou Flag ga Todomaru Tokoro wo Shiranai

Hirasawa Kazuki, an Ordinary Japanese Person, finds himself taking the place of Harold Stokes, a villain from the game Brave Hearts. He's a villain from a family of villains, so our new Harold can't take the usual path in these stories of suddenly reforming. Moreover, he is forced to speak like the 'real' Harold would--abrasively, derisively, rudely.

Available on Manga Box.